Liquid crystal composition, liquid crystal display and method of manufacturing liquid crystal display

ABSTRACT

There is provided a liquid crystal display including a first substrate, a second substrate facing the first substrate, and a liquid crystal layer intervening between the first and second substrates and containing liquid crystal substances different from each other, a sum of values each calculated from a formula: X α (RT log P α +HE α ) for all the liquid crystal substances in the liquid crystal layer being 32 kJ/mol or higher, wherein X α  denotes a molar fraction of a component α in the liquid crystal layer, P α  denotes a distribution ratio of the component α between an aqueous phase and a 1-octanol phase, HE α  denotes a hydration energy for 1 mol of the component α, R denotes a gas constant of 8.3 J/K·mol, and T denotes a temperature of 300 K.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2000-291905 filed Sep.26, 2000, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a liquid crystal composition, aliquid crystal display and a method of manufacturing the liquid crystaldisplay.

[0004] 2. Description of the Related Art

[0005] At present, a general liquid crystal display is manufactured inthe following procedure. First, an electrode and an alignment film aresuccessively formed on each of a pair of glass substrates havingswitching elements, a color filter layer, and the like. Subsequently,these glass substrates are disposed at a constant distance so that thealignment films are disposed opposite to each other, peripheries of theglass substrates excluding a liquid crystal sealing port are fixed withan adhesive, and a liquid crystal cell is formed. Additionally, a gapbetween the glass substrates is maintained to be constant by spacers.Thereafter, the gap between the liquid crystal cell is filled with aliquid crystal composition to form a liquid crystal layer, and theliquid crystal sealing port is sealed with a sealing material so thatthe liquid crystal display is obtained.

[0006] For the liquid crystal display manufactured by this method, whenthe liquid crystal layer is contaminated with an impurity, a displayproperty is largely influenced. However, the contamination with theimpurity cannot be avoided in the conventional liquid crystal display.Therefore, the conventional liquid crystal display has a problem thatdisplay unevenness occurs and reliability is deteriorated.

BRIEF SUMMARY OF THE INVENTION

[0007] According to a first aspect of the present invention, there isprovided a liquid crystal display comprising a first substrate, a secondsubstrate facing the first substrate, and a liquid crystal layerintervening between the first and second substrates and containingliquid crystal substances different from each other, a sum of valueseach calculated from a formula:

X_(α)(RT log P_(α)+HE_(α))

[0008] for all the liquid crystal substances in the liquid crystal layerbeing 32 kJ/mol or higher, wherein X_(α) denotes a molar fraction of acomponent α in the liquid crystal layer, P_(α) denotes a distributionratio of the component α between an aqueous phase and a 1-octanol phase,HE_(α) denotes a hydration energy for 1 mol of the component α, Rdenotes a gas constant of 8.3 J/K·mol, and T denotes a temperature of300 K.

[0009] According to a second aspect of the present invention, there isprovided a method of manufacturing a liquid crystal display, the displaycomprising a pair of substrates and a liquid crystal layer interveningbetween the substrates and containing liquid crystal substancesdifferent from each other, comprising determining a composition of theliquid crystal layer based on a sum of values each calculated from aformula:

X_(α)(RT log P_(α)+HE_(α))

[0010] for all the liquid crystal substances in the liquid crystallayer, wherein X_(α) denotes a molar fraction of a component α in theliquid crystal layer, P_(α) denotes a distribution ratio of thecomponent α, HE_(α) denotes a hydration energy for 1 mol of thecomponent α, R denotes a gas constant, and T denotes a temperature, andforming a structure comprising the liquid crystal layer interveningbetween the substrates and having the composition determined.

[0011] According to a third aspect of the present invention, there isprovided a liquid crystal composition comprising liquid crystalsubstances different from each other, a sum of values each calculatedfrom a formula:

X_(α)(RT log P_(α)+HE_(α))

[0012] for all the liquid crystal substances being 32 kJ/mol or higher,wherein X_(α) denotes a molar fraction of one component α of the liquidcrystal substances in the composition, P_(α) denotes a distributionratio of the component α between an aqueous phase and a 1-octanol phase,HE_(α) denotes a hydration energy for 1 mol of the component α, Rdenotes a gas constant of 8.3 J/K·mol, and T denotes a temperature of300 K.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0013]FIG. 1 is a sectional view schematically showing a liquid crystaldisplay according to an embodiment of the present invention; and

[0014]FIG. 2 is a schematic plan view of the liquid crystal displayshown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

[0015] The present inventors have investigated the reasons for theoccurrence of the display unevenness in a conventional liquid crystaldisplay. As a result, the present inventors have found that compoundscontained in an adhesive layer, a sealing material, spacers, aperipheral light shielding layer (or a picture-frame layer), a colorfilter layer, and the like, such as fatty acid, phenyl carboxylic acid,phenyl carboxylic acid derivative, phenylene dicarboxylic acid,phenylene dicarboxylic acid derivative, alkyl amine, phenylenediaminederivative, phenylene amine carboxylic acid, phenylene amine carboxylicacid derivative, and alkyl imide are eluted as impurities into a liquidcrystal layer, and then an illuminated defect, an alignmentirregularity, and an image persistence are generated. In more detail,when the impurities high in ionicity and/or polarity are eluted into theliquid crystal layer from a member in contact with the liquid crystallayer, an electric resistance value of a liquid crystal composition islowered (voltage holding ratio is deteriorated). Moreover, theimpurities eluted in the liquid crystal layer are adsorbed onto surfacesof alignment films. Therefore, display unevenness such as theilluminated defect, the alignment irregularity, and the imagepersistence occurs.

[0016] The present inventors have paid attention to the fact that mainlya polar impurity generates the display unevenness among the impuritieseluted into the liquid crystal layer, have considered that the displayunevenness can be inhibited from occurring by realizing a liquid crystalcomposition not easily causing mixture of the polar impurity, and haveintensively researched the composition. As a result, present inventorshave found that a value calculated from the following formula (1), whichtakes account of both hydrophobic and hydrophilic natures, has aremarkably high correlation with the occurrence of the displayunevenness. $\begin{matrix}{\sum\limits_{\alpha = 1}^{n}\quad {X_{\alpha}\left( {{{R \cdot T \cdot \log}\quad P_{\alpha}} + {HE}_{\alpha}} \right)}} & (1)\end{matrix}$

[0017] Additionally, in the above formula (1), X_(α) denotes a molarfraction of a component α in the liquid crystal composition, P_(α)denotes a distribution ratio of the component α, HE_(α) denotes ahydration energy per mol of the component α, R denotes a gas constant, Tdenotes a temperature, and n denotes the number of all components in theliquid crystal composition.

[0018] In the formula (1), the distribution ratio P_(α) is (wholeconcentration of the component α in an organic phase)/(wholeconcentration of the component α in a aqueous phase), and log P_(α) as alogarithm of the distribution ratio P_(α) is a hydrophobic parameter.Moreover, RT log P_(α) is proportional to a difference between a freeenergy of the organic phase containing a unit concentration of thecomponent α at the temperature T and a free energy of the aqueous phasecontaining a unit concentration of the component α at the temperature T.When the distribution ratio P_(α), the hydrophobic parameter log P_(α),or RT log P_(α) is large, the component α is easily dissolved in theorganic phase, and the component can therefore be considered to be morehydrophobic.

[0019] On the other hand, the hydration energy HE_(α) is an energychange obtained when one mol of component α, the molecules of which doesnot interact to each other, is infinitely diluted with water. That is,the hydration energy HE_(α) is equal to a difference between a latticeenergy and heat of dissolution (infinite dilution) of the component α.When the hydration energy HE_(α) is small, the component α can beconsidered to be more hydrophilic.

[0020] In this manner, RT log P_(α) and HE_(α) indicate the hydrophobicand hydrophilic natures of the component α. When a sum of these valuesindicates a larger value, the component α can be considered not toeasily cause the contamination by the polar impurity. That is, RT logP_(α)+HE_(α) indicates resistance of the component α to contamination bythe polar impurity. Therefore, the resistance of the liquid crystalcomposition to the contamination by the polar impurity can be judged bythe value calculated from the formula (1).

[0021] In the formula (1), the distribution ratio of the component αbetween the aqueous phase and the 1-octanol phase can be used as thedistribution ratio P_(α). In this case, a relatively high correlation isrealized between the value calculated from the formula (1) and theoccurrence of display unevenness. Moreover, in this case, where the gasconstant R and the temperature T are assumed to be 8.3 J/K·mol (2cal/K·mol) and 300 K, respectively, the display unevenness can beinhibited from occurring by setting the composition of the liquidcrystal composition such that the value calculated from the formula (1)is 32 kJ/mol (7.7 kcal/mol) or more, preferably 33.2 kJ/mol (8 kcal/mol)or more. Additionally, most of the liquid crystal substances whose valueof RT log P_(α)+HE_(α) is large are fluorine-based liquid crystalsubstances. In general, when a content of such a liquid crystalsubstance is large, a driving voltage tends to increase or a responsespeed tends to decrease. Therefore, the value calculated from theformula (1) is preferably 45.7 kJ/mol (11 kcal/mol) or less. It is notedthat the relation between the value and the effect hardly depends on thesize of the liquid crystal display, etc.

[0022] For the distribution ratio or the logarithm of the ratio, foundvalues are obtained with respect to many compounds, and experimentalparameters are sufficiently set. Moreover, it is known that the foundvalues agree with calculated values with a very high precision.Therefore, the distribution ratio P_(α) of the component α for use inthe formula (1) can be obtained by calculation. Furthermore, thehydration energy HE_(α)per mol of the component α can similarly beobtained by the calculation.

[0023] The calculation is usually performed with respect to a liquidcrystal molecule which has a most stable conformation. That is, it isnecessary to determine the most stable conformation of the liquidcrystal molecule before the calculation of the distribution ratio P_(α)and hydration energy HE_(α).

[0024] However, many liquid crystal molecules have not only a functionalgroup which can be considered as a rigid body such as an aryl group butalso a long-chain alkyl group which can constitute variousconformations. Additionally, the liquid crystal composition can containa large number of liquid crystal molecules, and can additionally containmolecules other than the liquid crystal molecules. Therefore, it usuallyrequires much time and labor to determine the most stable conformationand calculate the distribution ratio P_(α) and hydration energy HE_(α)based on the conformation with respect to the respective moleculesconstituting the liquid crystal composition.

[0025] The present inventors have studied in order to obtain a criteriawhich can be calculated in a simpler method and has a high correlationwith the occurrence of display unevenness. As a result, the presentinventors have found that a result similar to the aforementioned resultcan be obtained by a method in which the most stable conformation of theliquid crystal molecule is determined on regarding the alkyl grouphaving two or more carbon atoms as a normal pentyl group, thedistribution ratio P_(α) and hydration energy HE_(α) are calculatedbased on the conformation, the liquid crystal composition is assumed tobe constituted only of the liquid crystal molecules, and the formula (1)is utilized.

[0026] According to the method, the liquid crystal molecules whichdiffer from each other only in the number of carbon atoms of the alkylgroup are handled as the same liquid crystal molecule. Therefore, typesof molecules as objects of the calculation decrease. Moreover, since allthe alkyl groups each having two or more carbon atoms are regarded asthe normal pentyl groups, it is easy to determine the most stableconformation of the liquid crystal molecule.

[0027] Additionally, when the liquid crystal molecules differ from eachother in the number of carbon atoms of the alkyl group, the moleculesare considered to also differ from each other in the hydrophilic andhydrophobic natures. However, in many cases, the alkyl group having twoor more carbon atoms contained in the liquid crystal molecule has aboutthree to seven carbon atoms. Even when the alkyl group having two ormore carbon atoms is regarded as the normal pentyl group, a largedifference is not generated in a calculation result.

[0028] An example of the present invention will be described hereinafterwith reference to the drawings. Additionally, similar constitutingmembers in respective drawings are denoted with the same referencenumerals, and redundant description is omitted.

[0029] First, log P_(α), HE_(α), and RT log P_(α)+HE_(α) were calculatedby the following method with respect to plural types of liquid crystalsubstances having the normal pentyl group as shown in the followingTable 1. That is, the hydrophobic parameter log P_(α) and hydrationenergy HE_(α) of the liquid crystal substance α were calculated byHyperChem v5 manufactured by Hypercube Co. with a personal computerPV300 manufactured by Toshiba Corp. Concretely, first, molecular forcefield calculation (MM+) was used to obtain the most stable conformationof the liquid crystal molecule, and the hydrophobic parameter log P_(α)and hydration energy HE_(α) were calculated by experiential quantitativestructure-activity relationships (QSAR) program with respect to theliquid crystal molecules of the conformation. Additionally, thedistribution ratio P_(α) was regarded as the distribution ratio of theliquid crystal substance α between the aqueous phase and the 1-octanolphase. Results are also shown in Table 1. TABLE 1 Structure of liquid HERTlogP + HE crystal molecule log P (kcal/mol) (kcal/mol)

5.98 2.39 5.98

6.12 2.63 9.66

7.72 3.02 7.65

7.67 1.55 6.15

7.86 3.24 7.96

7.8 1.81 6.49

7.5 1.11 5.61

8.0 3.44 8.24

7.94 2.06 6.82

9.74 4.49 10.3

9.69 2.55 8.36

[0030] As shown in Table 1, in an ester-based liquid crystal, log P hasa large value, but HE has a small value, and RT log P+HE has arelatively small value. On the other hand, in a direct annular p-typeliquid crystal, with a larger number of rings, RT log P+HE has a largevalue, and the contamination of the polar impurity can more effectivelybe suppressed.

[0031] A liquid crystal display shown in FIGS. 1 and 2 was next used tocheck a relationship between the value calculated from the formula (1)and the display unevenness. Additionally, FIG. 1 is a partial sectionalview schematically showing the liquid crystal display according to anembodiment of the present invention. Moreover, FIG. 2 is a plan view ofthe liquid crystal display shown in FIG. 1. First, a structure of theliquid crystal display shown in FIGS. 1 and 2 will be described.

[0032] A liquid crystal display 1 shown in FIGS. 1 and 2 is a TN-typeliquid crystal display which can perform color display, and has astructure in which a liquid crystal layer 4 is held between an activematrix substrate 2 and an opposite substrate 3. A gap between the activematrix substrate 2 and opposite substrate 3 is maintained to be constantby a columnar spacer 5 formed on the active matrix substrate 2.Moreover, an adhesive layer 25 is disposed in a peripheral edge betweenthe substrates 2 and 3 except an injection port 26 for injecting aliquid crystal substance between the substrates 2 and 3, and a sealingmaterial 27 is used to seal the injection port 26. Additionally, theliquid crystal display 1 shown in FIGS. 1 and 2 is usually sandwichedbetween a pair of polarizers, and a light source is disposed on a backsurface side.

[0033] The active matrix substrate 2 has a transparent substrate 7 suchas a glass substrate, and coplanar type polysilicon TFT is formed on onemain surface of the transparent substrate 7. That is, an undercoatinglayer 8 having a two-layer structure of a silicon oxide film and siliconnitride film is formed on one main surface of the transparent substrate7. A semiconductor active layer (channel) 9 and high-concentrationimpurity regions 10 as source/drain are formed on the undercoating layer8, and a gate oxide film 11 is formed to cover the layer and theregions. Furthermore, a gate electrode 12 is formed on the gateinsulating film 11. Additionally, a scanning line (not shown) is formedin the same process as a process for forming the gate electrode 12.

[0034] A signal line 13 having a two-layer structure of Mo and Al layersis formed on the scanning line and gate insulating film 11. The signalline 13 is connected to the high-concentration impurity region 10 via acontact hole 15 formed through the gate insulating film 11 and aninterlayer insulating film 14.

[0035] An inorganic insulating film 16 having a two-layer structure of asilicon oxide film and silicon nitride film and a color filter layer 17are successively laminated on the signal line 13 and interlayerinsulating film 14. The color filter layer 17 has a stripe pattern ofthree colors of red, blue and green, which is formed by adding a colormaterial to a resin.

[0036] A pixel electrode 18 made of indium thin oxide (ITO) or anothertransparent conductive material is formed on the color filter layer 17.The pixel electrode 18 is electrically connected to TFT via a contacthole 19 formed in the color filter layer 17. Moreover, the columnarspacer 5 and a peripheral edge shield layer (not shown) are formed onthe color filter layer 17. An alignment film 20 of polyimide or the likeis formed on the pixel electrode 18 and columnar spacer 5.

[0037] The opposite substrate 3 has a structure in which a commonelectrode 22 and alignment film 23 are successively formed on thesurface of a transparent substrate 21 disposed opposite to the activematrix substrate 2. A voltage can be applied to the common electrode 22from the active matrix substrate 2 via an electrode transfer material(not shown) made of a silver paste or the like on a screen peripheralportion.

[0038] In the present example, the liquid crystal display 1 having astructure as described above was prepared by the following method.First, the glass substrate 2 with TFT, etc. formed on one main surfacethereof was prepared. Subsequently, a coating liquid for forming redcoloring layers was applied to the surface of the glass substrate 2 withTFT formed thereon. Next, a coating film obtained by the application ofthe coating liquid onto the transparent substrate 2 was patterned usingphotolithography and etching techniques. The film was patterned so thatportions of the coating film corresponding to a red color regions of thecolor filter layer 17 were left and the contact holes 19 were formed.The red coloring layers were obtained in this manner. Green and bluecoloring layers were successively formed by a similar process. Thereby,the 3 μm thick color filter layer 17 having striped coloring layers ofthree colors of red, blue and green was obtained. Additionally, thesecoloring layers were formed using ultraviolet hardening acrylic resinsCG-2000, CR-2000, and CB-2000 manufactured by Fuji Film Ourin Co. as thecoating liquid.

[0039] Next, a 100 nm thick ITO film was formed on the surface of theglass substrate 2 with the color filter layer 17 formed thereon by asputtering process, and the ITO film was patterned to obtain the pixelelectrodes 18.

[0040] Thereafter, a predetermined coating liquid was applied to thesurface of the transparent substrate 2 with the pixel electrodes 18formed thereon. Here, an ultraviolet hardening acrylic resin CK-2000containing a black pigment (manufactured by Fuji Hunt Technology Co.)was used as the coating liquid. Subsequently, the obtained coating filmwas patterned using the photolithography and etching techniques so thatthe columnar spacers 5 and peripheral light shielding layer were formed.

[0041] Subsequently, AL-1051 as polyimide manufactured by JSR Co. wasused to form a thin film on the surface of the glass substrate 2 withthe columnar spacers 5 and peripheral light shielding layer formedthereon, and the thin film was subjected to a rubbing treatment so thatthe alignment film 20 was obtained. The active matrix substrate 2 wascompleted as described above.

[0042] While the active matrix substrate 2 was prepared in theaforementioned method, the common electrode 22 of 100 nm thick ITO filmwas formed on one main surface of the glass substrate 21 and theopposite substrate 3 was prepared. The alignment film 23 was also formedon the common electrode 22 by a method similar to the aforementionedmethod.

[0043] Next, a thermosetting epoxy-based adhesive ES-5500 (manufacturedby Mitsui Toatsu Chemicals, Inc.) was used as the adhesive 25 to attachthe active matrix substrate 2 and opposite substrate 3 to each other anda liquid crystal cell was formed. Subsequently, the gap between theliquid crystal cell was filled with a predetermined liquid crystalcomposition via the injection port 26, and the sealing material 27 wasused to seal the injection port. The liquid crystal display 1 shown inFIGS. 1 and 2 was obtained as described above.

[0044] A plurality of liquid crystal displays 1 different from eachother in a type of the liquid crystal composition were prepared in theaforementioned method, and the value was obtained by calculation fromthe formula (1) with respect to each of the liquid crystal compositionsLCl to LC6. Additionally, as the hydrophobic parameter log P_(α) andhydration energy HE_(α), the value calculated by a method similar to theaforementioned method in which the alkyl group having two or more carbonatoms is regarded as the normal pentyl group was used, and the valueshown in Table 1 was also utilized. Moreover, it was assumed that thegas constant R was 2 cal/K·mol, the temperature T was 300 K, and theliquid crystal compositions LC1 to LC6 were constituted only by theliquid crystal molecules. Results are shown in the following Table 2.

[0045] Furthermore, a continuous lighting test was carried out for 1000hours under a high-temperature high-humidity condition of 60° C./80%with respect to the liquid crystal display 1 prepared by theaforementioned method. The results are also shown in Table 2. TABLE 2Liquid crystal ΣX_(α)(RTlogP_(α) + HE_(α)) composition (kcal/mol)Display unevenness LC1 8.2 Not occurred LC2 8.0 Occurred after 800 h LC37.7 Occurred after 500 h LC4 7.6 Occurred after 200 h LC5 7.2 Occurredafter 24 h LC6 7.0 Occurred at initial stage

[0046] As shown in the above Table 2, in the liquid crystal display 1using the liquid crystal compositions LC1 to LC3 in which the valuecalculated from the formula (1) was 7.7 kcal/mol or more, displayunevenness did not occur even after 300 hours. It was confirmed that thedisplay had a practically sufficient resistance.

[0047] Additionally, in the example, when the value was obtained by thecalculation from the formula (1), the calculation was simplified byregarding the alkyl group having two or more carbon atoms as the normalpentyl group. However, even when such simplification is not performed,the result can be obtained similarly as described above. Moreover, thehydrophobic parameter log P_(α) shown in Table 1 was obtained using thedistribution ratio P_(α) of the liquid crystal substance α between theaqueous phase and the 1-octanol phase. However, the hydrophobicparameter log P_(α) may be obtained using the distribution ratio P_(α)between the aqueous phase and another organic phase.

[0048] Furthermore, the liquid crystal display 1 structured as shown inFIGS. 1 and 2 has been described in the above example, but anotherstructure may also be employed. For example, in the example, thecoplanar polysilicon TFT was used as a switching element, but anotherTFT may also be used. Alternatively, color dot matrix display can alsobe performed by simple matrix driving. That is, a Y substrate having Yelectrodes each patterned in a band shape in a lateral (Y) direction onone main surface, and an X substrate having the color filter layer and Xelectrodes each patterned in the band shape in a longitudinal (X)direction successively laminated on one surface are disposed opposite toeach other so that the Y electrodes substantially cross at right anglesto the X electrodes, and the liquid crystal layer 4 is held between thesubstrates. This structure may also be employed. Furthermore, in theexample, the TN type liquid crystal display 1 has been described, butexamples of a display type may include an STN type, GH type, ECB type,and a type in which a ferroelectric liquid crystal is utilized.

[0049] Moreover, in the example, after the pixel electrode 18 wasformed, the columnar spacers 5 and peripheral light shielding layer wereformed. However, after the columnar spacers 5 and peripheral lightshielding layer are formed, the pixel electrode 18 may be formed.Furthermore, the columnar spacers 5 and peripheral light shielding layerwere simultaneously formed in the aforementioned method, but may also beformed in separate processes. Additionally, the columnar spacers 5 andperipheral light shielding layer were formed on the active matrixsubstrate 2 in the aforementioned method, but may also be formed on theopposite substrate 3. Alternatively, while one of the columnar spacers 5and the peripheral light shielding layer is formed on the active matrixsubstrate 2, and the other may be formed on the opposite substrate 3.

[0050] Moreover, in the example, a black-color photosensitivecomposition was used to form both of the columnar spacers 5 andperipheral light shielding layer, but may also be used to form only onethereof. Furthermore, the columnar spacers 5 may not have a shieldingproperty in the liquid crystal display 1. Additionally, plastic beads oranother grain spacers may also be used instead of the columnar spacers5.

[0051] As described above, in the present invention, the composition ofthe liquid crystal composition is set based on the value calculated fromthe predetermined formula in which both the hydrophobic and hydrophilicnatures of the liquid crystal composition are considered. Therefore, theliquid crystal composition which cannot easily be contaminated by thepolar impurity can be realized, and the display unevenness can thereforebe inhibited from occurring.

[0052] That is, according to the present invention, there are provided aliquid crystal composition which can realize a liquid crystal display inwhich the display unevenness does not easily occur and which has a highreliability, such a liquid crystal display, and a manufacturing methodof such a liquid crystal display.

[0053] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general invention concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A liquid crystal display comprising: a firstsubstrate; a second substrate facing the first substrate; and a liquidcrystal layer intervening between the first and second substrates andcontaining liquid crystal substances different from each other, a sum ofvalues each calculated from a formula: X_(α)(RT log P_(α)+HE_(α)) forall the liquid crystal substances in the liquid crystal layer being 32kJ/mol or higher, wherein X_(α) denotes a molar fraction of onecomponent α of the liquid crystal substances in the liquid crystallayer, P_(α) denotes a distribution ratio of the component α between anaqueous phase and a 1-octanol phase, HE_(α) denotes a hydration energyfor 1 mol of the component α, R denotes a gas constant of 8.3 J/K·mol,and T denotes a temperature of 300 K.
 2. The display according to claim1, wherein the first substrate comprises a color filter layer facing thesecond substrate, and pixel electrodes between the color filter layerand the liquid crystal layer.
 3. The display according to claim 1,wherein the first substrate comprises pixel electrodes facing the secondsubstrate, switching elements electrically connected to the pixelelectrodes, signal lines electrically connected to the switchingelements, and scanning lines crossing the signal lines, wherein thesecond substrate comprises a common electrode facing the firstsubstrate, and wherein either one of the first and second substratesfurther comprises a color filter layer facing another of the first andsecond substrates.
 4. The display according to claim 1, wherein the sumis 33.2 kJ/mol or higher.
 5. The display according to claim 1, whereinthe sum is 45.7 kJ/mol or higher.
 6. The display according to claim 1,wherein at least one of the liquid crystal substances comprises an alkylgroup which includes at least two carbon atoms, and wherein thedistribution ratio P_(α) and the hydration energy HE_(α) of the liquidcrystal substance which comprises the alkyl group are obtained supposingthat the alkyl group is an n-pentyl group.
 7. A method of manufacturinga liquid crystal display, the display comprising a pair of substratesand a liquid crystal layer intervening between the substrates andcontaining liquid crystal substances different from each other,comprising: determining a composition of the liquid crystal layer basedon a sum of values each calculated from a formula: X_(α)(RT logP_(α)+HE_(α))  for all components in the liquid crystal layer, whereinX_(α) denotes a molar fraction of a component α in the liquid crystallayer, P_(α) denotes a distribution ratio of the component α, HE_(α)denotes a hydration energy for 1 mol of the component α, R denotes a gasconstant, and T denotes a temperature; and forming a structurecomprising the liquid crystal layer intervening between the substratesand having the composition determined.
 8. The method according to claim7, wherein the determination of the composition is carried out to makethe sum be 32 kJ/mol or higher under a condition where the distributionratio P_(α) is a distribution ratio of the component α between anaqueous phase and a 1-octanol phase, the gas constant R is 8.3 J/K·mol,and the temperature T is 300 K.
 9. The method according to claim 7,wherein the determination of the composition is carried out to make thesum be 32.2 kJ/mol or higher under a condition where the distributionratio P_(α) is a distribution ratio of the component a between anaqueous phase and a 1-octanol phase, the gas constant R is 8.3 J/K·mol,and the temperature T is 300 K.
 10. The method according to claim 7,wherein the determination of the composition is carried out to make thesum be 45.7 kJ/mol or higher under a condition where the distributionratio P_(α) is a distribution ratio of the component α between anaqueous phase and a 1-octanol phase, the gas constant R is 8.3 J/K·mol,and the temperature T is 300 K.
 11. The method according to claim 7,wherein at least one of the liquid crystal substances comprises an alkylgroup which includes at least two carbon atoms, and wherein thedistribution ratio P_(α) and the hydration energy HE_(α) of the liquidcrystal substance which comprises the alkyl group are obtained supposingthat the alkyl group is an n-pentyl group.
 12. A liquid crystalcomposition comprising liquid crystal substances different from eachother, a sum of values each calculated from a formula: X_(α)(RT logP_(α)+HE_(α)) for all the liquid crystal substances being 32 kJ/mol orhigher, wherein X_(α) denotes a molar fraction of one component α of theliquid crystal substances in the composition, P_(α) denotes adistribution ratio of the component α between an aqueous phase and a1-octanol phase, HE_(α) denotes a hydration energy for 1 mol of thecomponent α, R denotes a gas constant of 8.3 J/K·mol, and T denotes atemperature of 300 K.
 13. The composition according to claim 12, whereinthe sum is 33.2 kJ/mol or higher.
 14. The composition according to claim12, wherein the sum is 45.7 kJ/mol or higher.
 15. The compositionaccording to claim 12, wherein at least one of the liquid crystalsubstances comprises an alkyl group which includes at least two carbonatoms, and wherein the distribution ratio P_(α) and the hydration energyHE_(α) of the liquid crystal substance which comprises the alkyl groupare obtained supposing that the alkyl group is an n-pentyl group.